Improved turf quality of transgenic bahiagrass (Paspalum notatum Flugge) constitutively expressing the ATHB16 gene, a repressor of cell expansion

Bahiagrass (Paspalum notatum Flugge) is a popular low-input turfgrass in subtropical regions. However, its turf quality and widespread use as residential turf is limited by up to 60-cm-tall seedheads and its open, sparse-looking growth habit. Plant growth retardants (PGRs) are being used in bahiagrass for the suppression of seedheads and leaf growth since a dwarf bahiagrass cultivar is not available and mowing costs are increasing. However, PGRs have to be applied frequently and may result in phytotoxicity. The improvement of turf quality by genetic engineering represents a promising alternative to the application of PGRs. The data presented here indicate that over-expression of the Arabidopsis ATHB16 transcription factor in bahiagrass significantly changes plant architecture of this important low-input turfgrass. All transgenic plants investigated produced significantly more vegetative and fewer reproductive tillers, shorter leaves and shorter tillers. Over-expression of ATHB16 resulted in a proportional reduction of leaf width and leaf length. The formation of seedheads under natural photoperiod was delayed in some transgenic lines for approximately 4 weeks. Total root or shoot biomass and seed set were not compromised in semi-dwarf bahiagrass plants over-expressing ATHB16. Our findings are consistent with the proposed function of ATHB16 as a suppressor of cell expansion and demonstrate its conserved role in grasses with direct practical implications for enhancing turf quality.